Vibrotactile intensity discrimination measured by three methods.
The difference threshold for the detection of changes in vibration amplitude was measured as a function of the intensity and frequency of stimuli delivered through a 2.9-cm2 contactor to the thenar eminence. Stimuli were either 25- or 250-Hz sinusoids, narrow-band noise centered at 250 Hz, or wideband noise. Thresholds were measured by two-interval, forced-choice tracking under three methods of stimulus presentation. In the gated-pedestal method, subjects had to judge which of two 700-ms bursts of vibration separated by 100 ms was more intense. In the continuous-pedestal method, subjects had to detect a 700-ms increment in the amplitude of an ongoing pedestal of vibration. In the two-burst-continuous-pedestal method with 1500-ms pedestals, the subject had to detect which of two successively presented pedestals contained a 500-ms amplitude increment. Thresholds were consistently lower for detecting increments in the amplitude of a continuous pedestal of vibration than for detecting amplitude differences between briefly presented successive pedestals or amplitude increments in successive pedestals. A "near miss" to Weber's law was found both for sinusoidal and for noise stimuli. The difference threshold was not affected by stimulus frequency condition.
Gescheider
G A
GA
Hamilton College, Clinton, New York 13323.
Bolanowski
S J
SJ
Verrillo
R T
RT
Arpajian
D J
DJ
Ryan
T F
TF
D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009475:Neurons, Afferent / Q000502:physiology*; D012684:Sensory Thresholds; D014110:Touch / Q000502:physiology*; D014732:Vibration